While you prepare AD it will create multiple container, objects and other items to store exchange configuration information in active directory. These collections of objects and container called “Exchange Org”.

This container will keep all of your exchange server and organization policy details this will help you to recover from server disaster.

Prepare Domains (PD): -

Setup.com /preparedomain ( setup.com /pd)

While you prepare domain, it will create a new OU “Microsoft Exchange Security Groups” in ADUC and multiple Exchange default security groups to administer the exchange environment.